By using the ac calorimetric technique we have developed a high-resolution experimental setup to study the thermoelectric power in a temperature range of 77 to 300 K. The system was tested using a chromel alloy (90% nickel, 10% chromium). Optical radiation was used to heat the sample periodically with a frequency of ω/2π = 1.5 Hz which induces temperature modulation Tac in one end of the sample. The induced emf Vac(T) between the illuminated and the dark sides of the sample was measured. The thermoelectric power S(T) was calculated from the relation Vac/Tac whose data points indicate an anomaly near 225 K. The temperature region of this anomaly agrees with that of the previously reported specific heat anomaly of chromel which is associated with the para- to ferroelectric phase transition in this Ni alloy.